2nd generation mobile communication refers to performing audio to digital transmission and reception. Herein, 2nd generation mobile communication includes CDMA (code Division Multiple Access), GSM (Global System for Mobile Communications), and so on. Also, GPRS (General Packet Radio Service) has been proposed as an evolved version of the GSM. Herein, the GPRS corresponds to a technology for providing packet switched data services based upon the GSM system.
3rd generation mobile communication refers to a communication technology enabling audio, video, and data transmission and reception. More specifically, 3GPP (Third Generation Partnership Project) has developed the mobile communication system (IMT-2000) technology and has adopted WCDMA (Wideband Code Division Multiple Access) as its Radio Access Technology (RAT). As described above, the IMT-2000 technology and the Radio Access Technology (RAT), e.g., WCDMA, are collectively referred to as a UMTS (Universal Mobile Telecommunication System) in Europe. Furthermore, UTRAN corresponds to an abbreviation for UMTS Terrestrial Radio Access Network.
Meanwhile, the 3rd generation mobile communication is evolving to a 4th generation mobile communication. The 4th generation mobile communication proposes a Long-Term Evolution Network (LTE) technology, which is currently being standardized by the 3GPP, and an IEEE 802.16 technology, which is currently being standardized by the IEEE (Institute of Electrical and Electronics Engineers). The term E-UTRAN (Evolved-UTRAN) is used in the LTE. The 4th generation mobile communication adopts OFDM (Orthogonal Frequency Division Multiplexing)/OFDMA (Orthogonal Frequency Division Multiple Access). The OFDM uses a plurality of orthogonal subcarriers. And, the OFDM uses a property of orthogonality between IFFT (Inverse Fast Fourier Transform) and FFT (Fast Fourier Transform). A transmitter performs IFFT on data, thereby transmitting the processed data. A receiver performs FFT on a received signal, thereby recovering the initial (or original) data. The transmitter uses IFFT in order to combine the plurality of subcarriers, and the receiver respectively uses FFT in order to separate (or divide) the multiple subcarriers.